One means of conveying particulate solids is in a conduit along with a flowing stream of gas, usually air, i.e., pneumatically conveying the particulate solids. The particulate solids generally need to be conveyed between various stages of processing. For example, polymer resin beads are pneumatically conveyed. It may be desirable to sample the particulate solids being pneumatically conveyed so that a chemical or physical analysis can be made of the particulate solid. Several samplers have been developed for this purpose.
Witherspoon et al, in U.S. Pat. No. 4,625,570, describe a device for removing samples of solid particulate dropped through a vertical pipeline. The device includes a scoop, i.e., a sample cup which can be telescoped into the pipeline through a side mounting track, attached to a flange on the pipeline, to catch a sample of the solid particulate in the scoop, and then telescoped out of the pipeline into the mounting track. The mounting track has a lower discharge opening which registers with the scoop when the latter is rotated 180 degrees so that the sample can be dropped into a container. The inner end of the scoop is closed so that the pipeline remains closed during all phases of the sampling operation. The Witherspoon et al device is designed for gravity conveyed particulate solids and is hand operated.
The Anacon Model 261 Automatic Sampler also uses a sample cup mounted on a probe that can be inserted and withdrawn from the conduit by a pneumatic actuator. The sample cup is equipped with a false bottom that can be withdrawn by another pneumatic actuator. In operation, the cup is inserted into the conduit and filled with the particulate solid. Then the cup is withdrawn from the conduit and positioned over an analyzer that directs a beam of near-infrared light onto the sample in the cup and thereby determines the moisture content of the sample by analyzing the near-infrared light reflected from the sample. The cup is then reinserted into the conduit and the false bottom withdrawn to return the sample to the process stream. The false bottom is then returned to collect another sample. The Anacon device is designed for gravity or pneumatically conveyed particulate solids and is automatic in operation.
When the Anacon device is installed in a pneumatic conveyer, operating at an average air velocity of about 80 feet per second, to collect samples of polymer beads so that the moisture content of the beads can be determined, a serious problem occurs, i.e., little or no sample is collected in the cup. Apparently, the air velocity is so high that the sample is blown out of the cup preventing the accumulation of any appreciable amount. The present invention overcomes this problem.